1. Field of the Invention
The present invention relates generally to illumination systems, and more specifically to a broadband energy illuminator.
2. Description of the Prior Art
Prior art security systems can be found at transportation centers such as airports, train stations, and other public transportation facilities. In addition, security systems are commonplace at courthouses, government buildings, or public schools to maintain public safety. One of the principal concerns of operators of security systems is the need to protect security personnel and other individuals (e.g. the general public) in the course of conducting a search of a person for concealed objects. The concealed objects that present a danger are weapons, explosives, contraband and other similar items that may endanger security personnel in proximity.
Prior art security systems include metal or chemical residue detectors that require security personnel to be in proximity of the individual. One or more security personnel are required to conduct a hands-on or “wand-based” scan of an individual for whom the metal or chemical residue detector has generated an alarm. An inherent deficiency of this type of security system is the fact that it exposes not only the security personnel to danger, but also other individuals (e.g., travelers in an airport) in the vicinity of the security system to the dangers posed by such concealed objects. Accordingly, there is a need in the relevant art for a security system that has the ability to perform from a stand-off perspective so that security personnel and innocent by-standers are not exposed to any potential threat or danger.
One type of system is a passive millimeter wave camera that has the ability to detect and image objects hidden under clothing. An ideal black material absorbs all the radiant energy and reflects none of the radiant energy to which it is being exposed. Since a “black body” is a perfect absorber of radiant energy, by the law of thermodynamics it must also be a perfect emitter of radiation. The distribution according to wavelength of the radiant energy of a black body radiator depends on the absolute temperature of the black body and not on its internal nature or structure. As the temperature increases, the wavelength at which the energy emitted per second decreases. This phenomenon can be seen in the behavior of an ordinary incandescent object, which gives off its maximum radiation at shorter and shorter wavelengths as it becomes warmer.
All objects are composed of continually vibrating atoms with the higher energy atoms vibrating more frequently. The vibration of all charged particles, including these atoms, generates electromagnetic waves. The higher the temperature of an object, the faster the vibration, and thus, the higher the spectral radiant energy. As a result, all objects are continually emitting radiation at a rate with a wavelength distribution that depends on the temperature of the object and its spectral emissivity.
Accordingly, the passive millimeter wave camera detects radiation that is given off by all objects. The technology works by contrasting the millimeter wave signature of the human body, which is warm and reflective, against that of a gun, knife or other contraband. Those objects appear dark because of the differences in temperature, hence, millimeter wave energy, between the human body and the inanimate objects.
The temperature of the human body is typically 98.6 degrees Fahrenheit. Therefore, when the ambient temperature is much less than the human body temperature, a millimeter wave camera detects the image of the human body fairly easily. However, when the ambient temperature approaches the range of the human body temperature, there appears to be less contrast between the human body and the background scene. This causes the image of the human body to be less defined and less effective in determining the targeted individual and concealed objects. There is no effective method that has been found to address the background scene blending of millimeter wave energy without using expensive cooling apparatus. Clearly there is a need in the art for an apparatus that improves the capability of a millimeter wave camera to operate effectively under relatively high ambient temperatures that is compact and inexpensive.
There is also a need in the art for an improved illumination system for use with a millimeter wave camera that is easy to operate.
It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed.
However, in view of the prior art at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.